The ad, part of a $200,000 statewide broadcast and cable television buy, follows similar allegations published in a report in the Arizona Republic last week. Immigration has been a prominent issue in Arizona's GOP Senate primary, with Cardon frequently accusing Flake of supporting "amnesty."

"In a business career spanning 20 years, Wil has never hired an illegal immigrant, nor has he ever condoned such a practice," Cardon spokeswoman Alyssa Pivirotto said in a statement. "That stands in stark opposition to Congressman Flake, who has long supported 'comprehensive immigration reform' and who opposed [Arizona's state immigration law]."

Cardon also launched a television ad this week criticizing Flake's positions on immigration, the debt ceiling and taxes.

"I'm a businessman who's balanced budgets and created jobs," Cardon says in the ad. "I'll work to get America moving in the right direction."